Factors controlling irregular flowering in four alpine species for Chionochloa

Irregular flowering occurs in at least nine alpine species of Chionochloa and, moreover, their flowering seasons usually coincide. Transplanting experime::lts with four of these species (C. crassiuscula, C. flavescens, C. oreophila and C. rigida) indicate that their flowering is largely controlled by the environment, although availability of reserves is probably also important.
The number of tillers induced in a tussock varies with the duration of high-temperature treatment received during the summer long-day period. Such a day-length-temperature control of flowering, involving a cumulative effect of relatively high temperatures received during long days, has not been recorded in any other grasses. In three species, synchronization of flowering over their altitudinal ranges is achieved by ecotypic differentiation in the temperature requirement.
The apparently rare phenomenon among grasses of autumn initiation and successful overwintering of inflorescences occurs in the four species studied.
The possible adaptive value of irregular flowering in alpine species of Chionochloa is discussed.